add evaluate handler

Author: TylerLeonhardt

src/PowerShellEditorServices.Engine/LanguageServer/OmnisharpLanguageServer.cs

@@ -116,6 +116,7 @@ public async Task StartAsync()
                     .WithHandler<DefinitionHandler>()
                     .WithHandler<TemplateHandlers>()
                     .WithHandler<GetCommentHelpHandler>()
+                    .WithHandler<EvaluateHandler>()
                     .OnInitialize(
                         async (languageServer, request) =>
                         {

src/PowerShellEditorServices.Engine/Services/PowerShellContext/Handlers/EvaluateHandler.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
+using Microsoft.PowerShell.EditorServices;
+
+namespace PowerShellEditorServices.Engine.Services.Handlers
+{
+    public class EvaluateHandler : IEvaluateHandler
+    {
+        private readonly ILogger _logger;
+        private readonly PowerShellContextService _powerShellContextService;
+
+        public EvaluateHandler(ILoggerFactory factory, PowerShellContextService powerShellContextService)
+        {
+            _logger = factory.CreateLogger<EvaluateHandler>();
+            _powerShellContextService = powerShellContextService;
+        }
+
+        public async Task<EvaluateResponseBody> Handle(EvaluateRequestArguments request, CancellationToken cancellationToken)
+        {
+            await _powerShellContextService.ExecuteScriptStringAsync(
+                request.Expression,
+                writeInputToHost: true,
+                writeOutputToHost: true,
+                addToHistory: true);
+
+            return new EvaluateResponseBody
+            {
+                Result = "",
+                VariablesReference = 0
+            };
+        }
+    }
+}

src/PowerShellEditorServices.Engine/Services/PowerShellContext/Handlers/IEvaluateHandler.cs

@@ -0,0 +1,44 @@
+using OmniSharp.Extensions.Embedded.MediatR;
+using OmniSharp.Extensions.JsonRpc;
+
+namespace PowerShellEditorServices.Engine.Services.Handlers
+{
+    [Serial, Method("evaluate")]
+    public interface IEvaluateHandler : IJsonRpcRequestHandler<EvaluateRequestArguments, EvaluateResponseBody> { }
+
+    public class EvaluateRequestArguments : IRequest<EvaluateResponseBody>
+    {
+        /// <summary>
+        /// The expression to evaluate.
+        /// </summary>
+        public string Expression { get; set; }
+
+        /// <summary>
+        /// The context in which the evaluate request is run. Possible
+        /// values are 'watch' if evaluate is run in a watch or 'repl'
+        /// if run from the REPL console.
+        /// </summary>
+        public string Context { get; set; }
+
+        /// <summary>
+        /// Evaluate the expression in the context of this stack frame.
+        /// If not specified, the top most frame is used.
+        /// </summary>
+        public int FrameId { get; set; }
+    }
+
+    public class EvaluateResponseBody
+    {
+        /// <summary>
+        /// The evaluation result.
+        /// </summary>
+        public string Result { get; set; }
+
+        /// <summary>
+        /// If variablesReference is > 0, the evaluate result is
+        /// structured and its children can be retrieved by passing
+        /// variablesReference to the VariablesRequest
+        /// </summary>
+        public int VariablesReference { get; set; }
+    }
+}

test/PowerShellEditorServices.Test.E2E/LanguageServerProtocolMessageTests.cs

@@ -781,5 +781,21 @@ await LanguageClient.SendRequest<CommentHelpRequestResult>(
             Assert.NotEmpty(commentHelpRequestResult.Content);
             Assert.Contains("myParam", commentHelpRequestResult.Content[7]);
         }
+
+        [Fact]
+        public async Task CanSendEvaluateRequest()
+        {
+            EvaluateResponseBody evaluateResponseBody =
+                await LanguageClient.SendRequest<EvaluateResponseBody>(
+                    "evaluate",
+                    new EvaluateRequestArguments
+                    {
+                        Expression = "Get-ChildItem"
+                    });
+
+            // These always gets returned so this test really just makes sure we get _any_ response.
+            Assert.Equal("", evaluateResponseBody.Result);
+            Assert.Equal(0, evaluateResponseBody.VariablesReference);
+        }
     }
 }